It is increasingly common for engines to be equipped with both high pressure exhaust gas recirculation (HP-EGR) and low pressure exhaust gas recirculation (LP-EGR). HP-EGR redirects exhaust gas from an exhaust passage upstream of a turbine and delivers the exhaust gas to an intake passage downstream of a compressor. Alternatively, LP-EGR redirects exhaust gas from the exhaust passage downstream of the turbine and delivers the exhaust gas to the intake passage upstream of the compressor. An advantage of LP-EGR over HP-EGR may be that LP-EGR drives the turbine before being redirected to the intake passage and as a result, energy is conserved.
However, there are difficulties associated with EGR, specifically LP-EGR. For example, when LP-EGR mixes with intake air and/or components within an intake system, water may condense in the intake air forming droplets or impinge onto surfaces of the components. This is due to a higher temperature of LP-EGR and a lower temperature of the intake system and/or intake air. In this way, the temperature of the air and/or intake system surfaces may be less than a dew point temperature of water vapors within the LP-EGR. Condensate droplets may lead to increased noise and/or possibly damage to compressor blades. Furthermore, as LP-EGR increases, condensate may also increase.
Attempts to address the above described problem include condensate collectors located within an LP-EGR passage as shown in U.S. Pat. No. 8,056,338 Joergi et. al. The condensate collectors may collect vapors from the LP-EGR before it flows into an intake passage. Furthermore, the condensate collected may be directed toward a compressor wheel in order to prevent erosion.
However, the inventors herein have recognized potential issues with such systems. As one example, the condensate collector does not mitigate condensation of vapors from intake air as well. By placing the collector in the LP-EGR passage, vapors in the intake air may condense onto intake surfaces and/or form condensate droplets. The condensate collector and a passage leading from the collector to the compressor wheel may lead to packaging restraints and thus the condensate collector may not be universal to all vehicles.
In one example, the issues described above may be addressed by a method for bypassing charge air to an intake system via a compressor bypass drawing charge air upstream and downstream of a compressor impeller and able to introduce the charge air at an angle acute to an inner wall of an intake passage via an annular outlet. In this way, the bypassed charge air may create a barrier between the inner wall of the intake passage and the charge air in order to mitigate condensate impinging onto the inner wall.
As one example, when LP-EGR is flowing into the intake passage, the compressor bypass may be activated in order to decrease a likelihood of condensate formation. Additionally or alternatively, the compressor bypass may be activated based on weather conditions (e.g., humidity, rain, snow, etc.). By doing this, the compressor bypass may decrease a likelihood of condensate droplets forming onto inner walls of the intake passage while also artificially increasing a charge air quantity provided to a compressor.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.